- Bloomsburg Formation
Infobox Rockunit
name = Bloomsburg Formation
type =Geological formation
prilithology =Siltstone
otherlithology =Shale ,Claystone ,Sandstone ,Limestone
namedfor =Bloomsburg, Pennsylvania
namedby =
region =Appalachian Basin of easternNorth America
caption = A hand sample of the Bloomsburg Siltstone fromPort Clinton, Pennsylvania
unitof =
subunits =
thickness = up to convert|5000|ft|m|-1Wood, G.H., Trexler, J.P., Kehn, T.M., (1964). Geology of the West-Central Part of the Southern Anthracite Field and Adjoining Areas, Pennsylvania. United States Geological Survey, C-46.]
extent = New York to Maryland
age =Late Silurian TheSilurian Bloomsburg Formation (Sb) is a mapped bedrock unit inPennsylvania ,New Jersey ,New York andMaryland . It is named for the Town ofBloomsburg, Pennsylvania for which it was first described. The Bloomsburg marked the first occurance of red sedimentary rocks in theAppalachian Basin . Early American geologists theorized that these beds correlated withOld Red Sandstone found inScotland ..]Description
The Bloomsburg is defined as a grayish-red and greenish-gray
claystone ,argillaceous siltstone ,shale , and very fine to fine-grainedsandstone ,cite web |url=http://www.dcnr.state.pa.us/topogeo/openfile/midsusque.pdf |title= Preliminary Bedrock Geologic Map of the Middle Portion of the Susquehanna River Valley, Cumberland, Dauphin, And Perry Counties, Pennsylvania |year=2007|accessdate=2008-01-26 |author= Jackson, Margaret S.; Hanley, Peter M.; and Sak, Peter B. |publisher=Pennsylvania Geological Survey |format=pdf |work=Open File Report OFBM-07-05.0] arranged infining-upward cycles. [Berg, T.M., Edmunds, W.E., Geyer, A.R. and others, compilers, (1980). Geologic Map of Pennsylvania: Pennsylvania Geologic Survey, Map 1, scale 1:250,000.] Although the Bloomsburg can sometimes be green to gray, its most dominant color is red and they are often called "The Bloomsburg Red Beds". This is significant in theAppalachian Basin since it marks the first large scale terrestrial collection of sediemnts in the rock record. Most of the sediments that were deposited before this time were marine, or a small scale terrestrial zone.Depositional Environment
The Bloomsburg is mostly
molasse resulting from theTaconic orogeny . The red color is often evidence that the sediments were deposited in arid conditions. The upper parts of the Bloomsburg are thought to be a marine transition zone.Hoskins, D.M., (1961). Stratigraphy and paleontology of the Bloomsburg Formation of Pennsylvania and adjacent states: G36. Pennsylvania Geologic Survey, Harrisburg, Pennsylvania.]Fossils
There are numerous fossils found in the Bloomsburg, mostly in the upper parts of the formation. There are trace fossils of early land plants and
brachiopod fossils in the upper marine transitional zones..]Age
Relative age dating of the Bloomsburg places it in the Upper
Silurian period, being deposited between 417 to 410 (±5) million years ago. It rests conformably a top theClinton Group cite web |url=http://www.dcnr.state.pa.us/topogeo/openfile/midsusque.pdf |title= Preliminary Bedrock Geologic Map of the Middle Portion of the Susquehanna River Valley, Cumberland, Dauphin, And Perry Counties, Pennsylvania |year=2007|accessdate=2008-01-26 |author= Jackson, Margaret S.; Hanley, Peter M.; and Sak, Peter B. |publisher=Pennsylvania Geological Survey |format=pdf |work=Open File Report OFBM-07-05.0] andShawangunk Formation , and has a complex upper contact. In eastern Pennsylvania and New Jersey, the upper part of the Bloomsburg marks theWallbridge Unconformity . As you move west, theWills Creek Formation lies conformably atop the Bloomsburg. Further west, the McKenzie Member of the Mifflintown Formation interfingers with the Bloomsburg and eventually, the Bloomsburg pinches out into the Mifflintown. [Berg, T.M., et al., (1983). Stratagraphic Correlation Chart of Pennsylvania: G75, Pennsylvania Geologic Survey, Harrisburg, Pennsylvania.]Economic uses
The Bloomsburg formation is a source of material for the manufacture of brick and other clay products, as well as a local building stone.cite paper|url=http://www.dcnr.state.pa.us/topogeo/openfile/mcalevysfort.pdf|format=pdf|author= Doden, Arnold G. and Gold, David P.|year=2008|title=Bedrock Geologic Map of The Mc Alevys Fort Quadrangle, Huntingdon, Centre, and Mifflin Counties, Pennsylvania|publisher=Pennsylvania Geological Survey]
References
ee also
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Geology of Pennsylvania
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